1. Field
One or more embodiments of the present invention relate to a coating composition, and a cooking device and/or a cooking receptacle coated with the same, and, more particularly, to a coating composition with favorable thermal resistance, acid resistance, mechanical strength and washability, as well as a cooking device and/or a receptacle coated with the same.
2. Description of the Related Art
Enamel is a coating formed by applying vitreous glazes to a surface of a metal. The enamel has combined properties including the toughness of a metal ingredient and the corrosion resistance and cleanliness of a glass ingredient and, therefore, is widely used in cooking devices and/or cooking receptacles.
Among coating materials used in the manufacture of cooking devices and/or cooking receptacles, Teflon materials such as polytetrafluorethylene (PTFE) are frequently used. Teflon has low surface energy and is typically only slightly smeared by water or oil contained in foods and, thus, exhibits excellent washability. However, this material has disadvantages such as: low thermal resistance that may cause difficulty in using the material at temperatures exceeding 250 degrees C.; low mechanical strength, which in turn, requires careful washing thereof; and decreased adhesion properties of a coating surface if repeatedly used.
In order to remove waste adhered to the coating surface, a catalytic enamel comprising SiO2, Na2O and MnO2 has been developed. This material is based on a principle that oils and/or impurities are absorbed into microfine pores of the catalytic enamel. Thus, the catalytic enamel must have the microfine pores to receive such impurities. The microfine pores of the catalytic enamel may lead to problems in that the catalytic enamel has an uneven surface, small surface strength and/or low abrasion resistance, may be easily released from a metal body to which the catalytic enamel is coated by external impact, and may adversely affect health since the impurities are accumulated in the microfine pores after long periods of use.
Conventional glazes show favorable adhesiveness to an oily surface, a polished surface and/or a layer to be coated with the glazes but disadvantageously exhibit poor thermal resistance. In particular, when continuously used at a temperature of at least 450° C., the enamel may encounter serious problems including, for example, cracks, scumming, loss of a glaze layer in the enamel, etc.
In recent years, therefore, pyrolytic enamels have been used to coat inner frames, a fan and/or a door of an oven, in particular, among different cooking devices, so as to achieve improved washability of the oven. The pyrolytic enamel may provide sufficient heat to the oven during cleaning thereof so as to burn and remove waste, in particular, oily waste adhered to an inner surface of the oven. Therefore, pyrolytic enamel typically has moderate thermal resistance sufficient to withstand high temperatures in the range of 450 to 500° C., at which waste, in particular oily waste, can be completely combusted. However, using the pyrolytic enamel, all parts of an oven structure (including a heat insulation material for the oven) must endure high temperature conditions. Also, even if the oven temperature is raised to the range of 450 to 500° C., the entire oven does not typically reach the temperature in the range of 450 to 500° C. Especially at corners and/or at other portions near the door the temperature does not reach the temperature range of 450 to 500 and, therefore, the waste still remains thereon. In order to solve this problem, it may be proposed to continuously maintain the temperature of the entire oven at 500° C. or more so that the temperature of the corner parts and/or the portions near the door part can be increased to the range of 450 to 500° C. However, this approach causes a problem in that other parts of the oven may malfunction or suffer damage due to the high temperature.
TABLE 1constitutional compositions of conventional enamelsNormal enamelCatalyticPyrolyticComponents(wt. %)enamel (wt. %)enamel (wt. %)SiO230~60 10~60 10~60 Na2O5~200~20 0~20K2O0~200~20 0~20CaO0~100~100~5BaO0~100~100~5MgO0~5B2O30~20 0~20Al2O30~100~5TiO20~20 0~10P2O50~100~100~5Li2O0~100~10 0~10Sb2O30~20ZnO0~5 0~200~5ZrO20~5 0~5Co2O30~3 0~3NiO0~3 0~3MnO20~2 0~500~2CuO0~2 0~2